With magnificent views of Boston Harbor and the city skyline, this Nahant guest cottage is a summer haven. The owners, who have a larger home on the property, hired Lian Eoyang, a San Francisco-based designer trained as an architect, to draft plans for the 1,200-square-foot structure, where a dilapidated shed had stood. Eoyang created a striking fieldstone facade from ledge gleaned during excavation. “The place was birthed from its surroundings,” says Eoyang. “The interior imparts the feeling of openness and prominence toward the cove over which it stands.” In the great room, the ceiling is more than 10 feet high, and a large window erases the boundary between inside and outside. “The idea with the decor was to ‘set it and forget it,’ ” says Eoyang. Stylish modern furnishings are paired with inexpensive pieces and antiques, creating a calmly elegant vibe.